ioredfour

Originally forked from redfour. Main difference being that redfour uses node_redis + node-redis-scripty while ioredfour uses ioredis.

Install

or

npm install ioredfour --save

Usage example

const Lock = require('ioredfour');

(async () => {
    const testLock = new Lock({
        // Can also be an `Object` of options to pass to `new Redis()`
        // https://www.npmjs.com/package/ioredis#connect-to-redis, or an existing
        // instance of `ioredis` (if you want to reuse one connection, though this
        // module must create a second).
        redis: 'redis://localhost:6379',
        namespace: 'mylock',
        // Don't consider the lock owned until writes have been replicated at least this many times
        minReplications: 1,
        // Wait at most this many miliseconds for replication
        replicationTimeout: 500
    });
    const id = Math.random();

    // First, acquire the lock.
    const firstlock = await testLock.acquireLock(id, 60 * 1000 /* Lock expires after 60sec if not released */).catch(e => {
        console.log('error acquiring first lock', e);
    });
    if (!firstlock.success) {
        console.log('lock exists', firstlock);
    } else {
        console.log('lock acquired initially');
    }

    // Another server might be waiting for the lock like this.
    testLock
        .waitAcquireLock(id, 60 * 1000 /* Lock expires after 60sec */, 10 * 1000 /* Wait for lock for up to 10sec */)
        .then(secondlock => {
            if (secondlock.success) {
                console.log('second lock acquired after wait!', secondlock);
            } else {
                console.log('second lock not acquired after wait!', secondlock);
            }
        })
        .catch(e => {
            console.log('error wait acquiring', e);
        });

    // When the original lock is released, `waitAcquireLock` is fired on the other server.
    setTimeout(async () => {
        try {
            await testLock.releaseLock(firstlock);
            console.log('released lock');
        } catch (e) {
            console.log('error releasing', e);
        }
    }, 10 * 1000);
})();

Contributing

We welcome pull requests! Please lint your code.

Release History

• 1.1.0 add Lock.extend, promisified interface, check for replication
• 1.0.2-ioredis Forked from redfour and switch node_redis with ioredis
• 1.0.2 Don't use instanceof to determine if the redis constructor option is of type redis.RedisClient.
• 1.0.1 Fix issue where you could only pass in a Redis connection URI.
• 1.0.0 Initial release.

Etymology

Shortened (and easier to pronouce) version of "Redis Semaphore"